In order to achieve drainage of these waste waters, it is known to connect the drain of sinks and of ice cube drawers with a drainage circuit extending inside the aircraft as far as the fuselage of the aircraft. The drainage circuit is extended by a drain mast, attached on the skin of the fuselage on the outside of the aircraft and allowing discharge of waste waters on the outside of the aircraft.
For example the aircraft is provided with two drain masts: a first mast, located at the front of the aircraft, receives the waste waters from sinks and ice cube drawers, and a second mast, located at the rear of the aircraft, only receives waste waters from sinks.
Typically, a drain mast comprises a fairing attached onto the skin of the fuselage of the aircraft and a drainage conduit extending inside the fairing between an upstream end connected to the drainage circuit of the aircraft and a downstream end through which water is discharged on the outside of the aircraft.
The waters from the drainage of sinks are discharged in the form of a flow of a more or less significant amount of water, flowing sporadically and according to the use of the sinks.
Conversely, the waters from ice cube drawers are discharged as a permanent dropwise flow which is similar to seepage.
In order to facilitate the flow of this seepage, an air flow for example from a permanent leak from the pressurized cabin, is injected into the drainage line from the trickler as far as the drainage conduit.
Moreover, the waste waters tend to freeze upon their discharge through the drainage conduit, because of the low temperature of the atmosphere around the flying aircraft (of the order of −55° C. at the cruising altitude).
In order to attempt to solve this problem, it is known how to provide the drainage conduit with heating elements, for example comprising a heating wire wound around the drainage conduit. The electric power powering these heating elements should be limited, in order to avoid any risk of overheating when the aircraft is on the ground, which may cause melting of the fairing.